1. Field of the Invention
This invention relates to electronic circuits, and more particularly, to dynamic logic circuits.
2. Description of the Related Art
Dynamic logic circuits are well known in the electronic arts as logic circuits that operate according to a cycle of a clock signal. A first phase of the clock cycle (e.g., when the clock signal is low) may be a precharge (or pre-discharge) phase, whereas a second phase of the clock cycle is an evaluation phase. During the precharge phase of a circuit that utilizes the same, certain nodes of a dynamic circuit may be precharged to a logic high level. During the evaluation phase, the precharged nodes may either remain at a logic high level or be discharged to a low level, depending on a logical evaluation of the inputs. For a circuit that utilizes a pre-discharge instead of a precharge, the operation may be similar to that described above, although the logic/voltage levels may be reversed.
Many types of circuitry may be implemented using dynamic logic circuitry. Memory circuits within a processor (e.g., cache memories) are one such application that may utilize dynamic logic. Such memories may include storage cells, corresponding bit lines coupled to the storage cells, precharge circuits coupled to the bit lines, and corresponding input circuits coupled to the other end of the bit lines. Write operations may be conducted according to the normal operation of dynamic logic circuitry. During a precharge phase of a write cycle, the bit lines may be precharged to a logic high level. When the evaluation phase begins, a data value may cause the bit line to either discharge or retain its value, depending on the data it has received. The resulting state of the bit line may be written into the storage cell.
While the use of dynamic logic circuits may be useful in some situations, the precharging of bit lines may have certain drawbacks. Since all conductors have a certain amount of capacitance, precharging bit lines implemented using long wires may consume more power for both precharging and discharging. Furthermore, as the capacitance of a wire increases, the amount of time to precharge and discharge the wire also increases.